Ultralife 9V Lithium batteries come in 2 different versions; FP and J.
The FP version has a plastic jacket and comes in a foil pack and is best for use in wireless microphones, medical devices and other indoor applications. If you're not sure which version to buy we recommend the FP version linked below.
The J version, listed here, is the same as the FP but has an aluminum jacket over the plastic casing and is best for use in smoke detectors, home security, parking meters and other outdoor applications where significant changes to temperatures or humidity might be experienced. The J version is slightly larger than a typical 9 volt so the FP version should be used in applications where the device cavity is tight. The J version comes packaged on a retail card.

Ultralife U9VL-J batteries are available in 3 different packages - the batteries themselves are identical:

This battery can be used in all types of applications including cordless microphones. One of the advantages of using a 9V Lithium battery versus an Alkaline battery is that a Lithium battery handles varying temperature ranges much better than an Alkaline battery. In addition a 9V Lithium battery, stored at room temperature, will give you up to a 10 year shelf life!!

CAUTION: Never touch the connectors at the top of one battery to that of another; the battery will short out and will be unusable.